Plasma etching apparatus

ABSTRACT

A plasma detector is provided inside an upper electrode of a parallel plate type dry-etching apparatus. Upon reaching a particular pressure at the detector, the etching apparatus is deactivated. This deactivation may be used to replace an ineffective gas introducing plate. The plasma detector measures a pressure of the plasma at the backside of the gas-introducing plate, which has gas holes therein. As the gas holes increase during use of the apparatus, the pressure of the plasma at the backside of the gas increases, and the function of the apparatus is comprised. By detecting the pressure of the plasma, defective conditions in the apparatus may be detected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure of an apparatus (plasmaetching apparatus) for manufacturing a semiconductor device.

2. Description of the Related Art

The interior of a processing chamber in a conventional etching apparatuscomprises an upper electrode 6 for supplying gas, and a lower electrode7 on which a wafer corresponding to an object to be etched is placed. Adescription will be made of it below with reference to FIG. 1.

The upper electrode 6 comprises a cooling plate 2 provided with gassupply holes 1 defined therein, a gas-introducing plate 4 provided witha plurality of gas holes 3 defined therein, and a jig 5 for fixing thegas-introducing plate 4 to the cooling plate 2. A wafer 8 correspondingto an object to be etched can be placed on the lower electrode 7. Uponactual etching, high-frequency power is supplied between the upperelectrode 6 and the lower electrode 7. In doing so, plasma is generatedto etch the wafer 8. The etching is carried out within anetching-processing chamber 9.

Now, the gas-introducing plate 4 introduces the gas discharged throughthe gas supply holes 1 defined in the cooling plate 2 in plural formonto the wafer 8. The gas-introducing plate 4 is a consumable good andhas the need for its regular replacement.

When the gas-introducing plate 4 lying within the processing chamber ofthe etching apparatus is used up, the gas-introducing plate 4 becomesthin as shown in FIG. 5. Further, the gas holes 3 defined in thegas-introducing plate increase in size. When the gas holes 3 of thegas-introducing plate 4 reach a given size or more respectively, thefollowing would occur. Plasma enters the backside (cooling plate side)of the gas-introducing plate from the etching-processing chamber 9through the enlarged gas holes 3. Designated at numeral 10 in FIG. 5typically illustrates the entrance of the plasma into the backside ofthe gas-introducing plate 4. When the plasma enters therein, the stateof discharge of the plasma on the wafer side becomes unstable. As aresult, an etching characteristic is deteriorated and the wafer 8 isunusually processed.

Further, the occurrence of the plasma in the backside of thegas-introducing plate 4 is not limited to the aforementioned case. Theplasma is generated even in a case where pressure in an apparatus variesand a case where the amount of supply of high-frequency power varies,for example.

Further, when a plasma discharge is kept long on the backside of thegas-introducing plate 4, particles are produced depending on reactants.There is a possibility that the wafer will be contaminated with theproduced particles.

Accurately recognizing when the gas-introducing plate 4 needs replacing,allows the solution of such a problem as described above.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an apparatus formanufacturing a semiconductor device, which is capable of accuratelyrecognizing when a gas-introducing plate of an upper electrode needsreplacing, and detecting even etching trouble.

According to the present invention, for achieving the above object, anupper electrode of a parallel-plate type dry etching apparatus isconfigured as follows: Means for detecting plasma is provided inside theupper electrode for supplying gas.

Described more specifically, the upper electrode comprises a coolingplate having a plurality of gas supply holes for supplying the gas, agas-introducing plate having gas holes for introducing the gas into asemiconductor wafer, a jig for fixing the gas-introducing plate to thecooling plate, and a sensor for detecting plasma. Thus, when the gasholes of the gas-introducing plate increase in size with their wearingand hence the plasma is generated on the backside of the gas-introducingplate, the sensor for detecting the plasma serves. At this point intime, the etching apparatus is deactivated.

In the present invention as well, means for detecting pressure isprovided inside an upper electrode for supplying gas, of aparallel-plate type dry etching apparatus.

Described more specifically, the upper electrode comprises a coolingplate having a plurality of gas supply holes for supplying the gas, agas-introducing plate having gas holes for introducing the gas into asemiconductor wafer, a jig for fixing the gas-introducing plate to thecooling plate, and a sensor for detecting pressure. Thus, when the gasholes of the gas-introducing plate increase in size with their wearingand hence the plasma is generated on the backside of the gas-introducingplate, the pressure sensor detects a reduction in pressure. At thispoint in time, the etching apparatus stops operating.

Further, in the present invention, first pressure detecting means isprovided inside an upper electrode for supplying gas, of aparallel-plate type dry etching apparatus. Second pressure detectingmeans is provided within an etching-processing chamber in which a waferis placed.

Described more specifically, the first pressure detecting means and thesecond pressure detecting means are connected to detect the differencebetween pressure detected by the first pressure detecting means andpressure detected by the second pressure detecting means. When gas holesof a gas-introducing plate increase in size with their wearing and henceplasma is generated on the backside of the gas-introducing plate, areduction in the difference between pressure inside the upper electrodeand pressure inside the etching-processing chamber is detected. At thispoint in time, the etching apparatus is stopped.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, it is believed that the invention, the objects and featuresof the invention and further objects, features and advantages thereofwill be better understood from the following description taken inconnection with the accompanying drawings in which:

FIG. 1 is a diagram showing a cross-section of a conventionalsemiconductor device manufacturing apparatus in which a gas-introducingplate is less worn;

FIG. 2 is a diagram illustrating a cross-section of a conventionalsemiconductor device manufacturing apparatus in which a gas-introducingplate increases markedly in wear;

FIG. 3 is a diagram depicting a cross-section of an apparatus formanufacturing a semiconductor device, according to a first embodiment ofthe present invention;

FIG. 4 is a diagram showing a cross-section of an apparatus formanufacturing a semiconductor device, according to a second embodimentof the present invention; and

FIG. 5 is a diagram illustrating a cross-section of an apparatus formanufacturing a semiconductor device, according to a third embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFFERED EMBODIMENTS

Respective embodiments of the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings. In therespective embodiments, the same elements or components are identifiedby like reference numerals.

First Embodiment

FIG. 1 shows a processing chamber of an etching apparatus according to afirst embodiment of the present invention. It is identical in basicconfiguration to a conventional one. In the conventional etchingapparatus, such a device as to detect a plasma was not placed on thebackside (on the cooling plate 2 side in FIG. 1) of a gas-introducingplate 4. In the first embodiment, a plasma detector 11 is placed on thebackside of the gas-introducing plate 4. A commercially availabledetector may be used as the plasma detector 11. It is however desirableto use a high-sensitive plasma detector capable of detecting even slightplasma. Further, the plasma detector 11 is placed in a position where itis most easy to detect the plasma.

As shown in FIG. 1, the plasma is stably generated while the normaletching process is being carried out. However, when the etching processis done many times, the gas-introducing plate is also etched. Thus, thethickness of the gas-introducing plate 4 becomes thinner. Further, gasholes 3 defined in the gas-introducing plate increase in size. When thesizes of the gas holes 3 defined in the gas-introducing plate 4respectively reach more than a predetermined size, the plasma isintroduced into the reverse side of the gas-introducing plate 4 throughthe gas holes 3.

The high-sensitive plasma detector 11 detects the slight plasmaintroduced into the backside of the gas-introducing plate. 4. Next, theetching apparatus is deactivated. Further, the plasma detector 11notifies the gas-introducing plate to be replaced by another to one.

When gas leaks within an etching-processing chamber 9, pressure varieson the backside of the gas-introducing plate 4. Plasma is generated onthe backside of the gas-introducing plate according to such a pressurefluctuation. Even in this case, the generated plasma is detected by theplasma detector. Further, the etching apparatus is brought to a halt.The cause of the leakage of the gas within the etching-processingchamber becomes apparent.

Further, when the amount of supply of high-frequency power varies,abnormal or improper etching is done. At this time, the state ofdischarge of the plasma becomes unstable. Further, plasma is generatedon the backside of the gas-introducing plate. Even in this case, thegenerated plasma is detected by the plasma detector 11. Then, theetching apparatus is brought to a halt.

In either case referred to above, the slight plasma generated on thebackside of the gas-introducing plate 4 is detected by thehigh-sensitive plasma detector 11. Then, the etching apparatus isdeactivated. Afterwards, the etching apparatus is checked. Thus, thecause of a malfunction thereof is removed.

As described above, the high-sensitive plasma detector 11 is placed onthe backside of the gas-introducing plate 4. The plasma generated on thereverse side of the gas-introducing plate 4 is detected with highaccuracy. The etching apparatus is deactivated simultaneously with thetime when defective conditions are detected. Further, the worn-outgas-introducing plate 4 is reliably replaced with another. Thus, a wafer8 can be prevented from being abnormally etched due to the wearing-outof the gas-introducing plate 4. Further, since the gas-introducing plate4 can be used up to its limit, it can be reduced in cost.

Second Embodiment

FIG. 4 is a diagram showing a second embodiment. In the secondembodiment, the plasma detector 11 employed in the first embodiment isreplaced by a pressure gauge 12.

Any pressure measuring apparatuses were not conventionally installed onthe backside (on the cooling plate 2 side in FIG. 4) of thegas-introducing plate 4. In the present embodiment, the pressure gauge12 is provided thereat. The pressure gauge 12 may be one now on themarket. It is desirable that a high-accuracy pressure gauge capable ofcapturing a slight fluctuation in pressure is used.

While normal etching is being carried out within an etching-processingchamber 9, no plasma enters the backside of the gas-introducing plate 4.However, when the gas-introducing plate 4 is used up, gas holes 3defined in the gas-introducing plate 4 increase in size. When the sizeof each gas hole 3 exceeds a predetermined size, the plasma enters theback of the gas-introducing plate 4. In doing so, a fluctuation inpressure occurs on the backside of the gas-introducing plate.

Even when trouble occurs in the etching-processing chamber and hence thestate of the plasma becomes unstable, the plasma is generated on thebackside of the gas-introducing plate. As the occurrence of defectiveconditions, may be mentioned a case in which a fluctuation in pressuredue to leaks occurs, a case in which the amount of supply ofhigh-frequency power varies, etc. In a manner similar to the above evenin these cases, a pressure fluctuation occurs on the backside of thegas-introducing plate.

While the etching is being carried out in a normal state, the backside(cooling plate 2 side) of the gas-introducing plate 4 is higher than theetching-processing chamber 9 in pressure. This is because gas is alwayssupplied from gas supply holes 1 defined in the cooling plate 2 inplural form on the backside of the gas-introducing plate 4. On the otherhand, since the gas reacted by etching is always exhausted from theetching-processing chamber 9, the pressure is relatively low. When theplasma enters the back of the gas-introducing plate 4 or is generated onthe backside thereof, the pressure changes and is caused to transitionfrom its high state to its low state. The pressure gauge 12 detects sucha change in pressure. When the detected pressure is lower than setpressure, the etching apparatus is deactivated.

Owing to the provision of the high-accuracy pressure gauge 12 on thebackside of the gas-introducing plate 4 as described above, thefluctuation in pressure is detected with high accuracy. The etchingapparatus is stopped simultaneously with the time when the defectiveconditions are detected. Thus, the wasted gas-introducing plate isreliably replaced by another.

Thus, a wafer can be prevented form being abnormally etched due tooverusing of the gas-introducing plate 4. Since the gas-introducingplate 4 can be used to its limitation, a reduction in cost thereof canbe achieved.

Further, since the pressure gauge 12 employed in the present embodimentis cheaper than the plasma detector 11 employed in the first embodiment,a further reduction in cost can be achieved.

Third Embodiment

FIG. 5 is a diagram showing a third embodiment. In the third embodiment,the plasma detector 11 employed in the first embodiment is replaced by afirst pressure gauge 13. Further, a second pressure gauge 14 is placedin an etching-processing chamber 9.

A pressure measuring device has heretofore been not installed on thebackside (on the cooling plate 2 side in FIG. 5) of the gas-introducingplate 4. In the present embodiment, the first pressure gauge 13 isprovided on the backside thereof. Further, the second pressure gauge 14is placed even in the etching-processing chamber 9. These first andsecond pressure gauges may be ones now on the market. It is howeverdesirable that a high-accuracy pressure gauge capable of capturing evena slight fluctuation in pressure is used. The first and second pressuregauges are not intended only for their single detection of pressurefluctuations. Detecting means 15 capable of detecting the difference inpressure between the respective pressure gauges is provided.

While normal etching is being carried out in the etching-processingchamber 9, no plasma enters the backside of the gas-introducing plate 4.However, when the gas-introducing plate 4 is used up, gas holes 3defined in the gas-introducing plate 4 increase in size. When the sizeof each gas hole 3 exceeds a predetermined size, the plasma enters theback of the gas-introducing plate 4. In doing so, the difference betweenpressure on the backside of the gas-introducing plate and pressure lyingwithin the etching-processing chamber 9 becomes small.

Even when trouble occurs in the etching-processing chamber and hence thestate of the plasma becomes unstable, the plasma is generated on thebackside of the gas-introducing plate. As the occurrence of defectiveconditions, may be mentioned a case in which a fluctuation in pressuredue to leaks occurs, a case in which the amount of supply ofhigh-frequency power varies, etc. In a manner similar to the above evenin these cases, the difference between the pressure on the backside ofthe gas-introducing plate 4 and the pressure within theetching-processing chamber 9 becomes small.

While the etching is being carried out in a normal state, the differencebetween the pressure on the backside (cooling plate 2 side) of thegas-introducing plate 4 and the pressure in the etching-processingchamber 9 increases. This reason is as follows: The pressure is highbecause gas is always supplied from gas supply holes defined in thecooling plate 2 in plural form on the backside of the gas-introducingplate 4. On the other hand,.since the gas reacted by etching is alwaysexhausted from the etching-processing chamber 9, the pressure is low.When the plasma enters the backside of the gas-introducing plate 4 andis generated on the backside thereof, the difference in pressurereferred to above changes from its large state to its small state. Thischange is detected by the first and second pressure gauges and thedetecting means 15. When the difference in pressure is lower than a setpressure difference, the etching apparatus is deactivated.

Owing to the provision of the first and second pressure gauges on thebackside of the gas-introducing plate 4 and within theetching-processing chamber 9 respectively and the provision of thedifference-in-pressure detecting means 15 as described above, thedifference between the pressure on the backside of the gas-introducingplate 4 and the pressure lying within the etching-processing chamber 9is detected with extremely high accuracy. Thus, highly-sensitivedetection can be achieved as compared with the second embodiment. Theetching apparatus is deactivated simultaneously with the time when thedefective conditions are detected. The wasted gas-introducing plate 4 isreliably replaced by another.

Accordingly, a wafer 8 can be prevented form being abnormally etched dueto overusing of the gas-introducing plate 4. Since the gas-introducingplate 4 is used to its limitation, a reduction in cost thereof can beachieved.

Further, since the second pressure gauge 14 is provided even in theetching-processing chamber in the present embodiment, a fluctuation inpressure in the etching-processing chamber can be detected. It ispossible to detect not only defective conditions caused by thegas-introducing plate but also etching trouble in the etching-processingchamber. This etching trouble includes, for example, a case in which thestate of plasma becomes non-uniform, a case in which a wafer cooling gasleaks within the etching-processing chamber 9, etc.

While the present invention has been described with reference to theillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Various modifications of the illustrativeembodiments, as well as other embodiments of the invention, will beapparent to those skilled in the art on reference to this description.It is therefore contemplated that the appended claims will cover anysuch modifications or embodiments as fall within the true scope of theinvention.

1-7. (canceled)
 8. An apparatus for etching a wafer, comprising: anupper gas electrode, which has a cooling plate provided with gas supplyholes and a gas-introducing plate with a plurality of gas holes; a lowergas electrode over which the wafer is placed; a first pressure gauge,which detects a first pressure between the cooling plate and thegas-introducing plate; a second pressure gauge, which detects a secondpressure between the gas-introducing plate and the lower electrode; anda detector, which detects a difference between the first pressure andthe second pressure, and which terminates the etching of the wafer whenthe difference in the pressures is greater than a predetermined value.9. An apparatus as recited in claim 8, wherein said upper gas electrodefurther comprises a jig, which fixes said gas-introducing plate to saidcooling plate.
 10. An apparatus as recited in claim 8, wherein saidfirst pressure gauge is provided between said gas-introducing plate andsaid cooling plate.
 11. An apparatus as recited in claim 8, wherein saidfirst pressure increases as said gas holes of said gas-introducing plateincrease in size.
 12. An apparatus as recited in claim 9, wherein saidfirst pressure gauge is at a backside of said gas introducing plate.